Froth from Foreign Office in the morning (4)
I believe the answer is:
foam
'froth' is the definition.
(I know that froth can be written as foam)
'foreign office in the morning' is the wordplay.
'foreign office' becomes 'FO' (abbreviation).
'in the morning' becomes 'am' (short for ante meridiem - before noon).
'fo'+'am'='FOAM'
'from' is the link.
(Other definitions for foam that I've seen before include "Lather, froth" , "Bubbles on liquid" , "Froth created by wave or soap" , "Suds" , "Froth or spume" .)